Replaced my upper control arm due to bad ball joint. Car drove fine before. Now I have a vibration at 30mph. Goes away at 40mph. I did not move/rotate tires. Why would vibration appear? Changing arm requires unbolting top of strut to move it away from arm bolts. Easy job. Took 1/2 hr.

I believe the steering wheel was off slightly compared to Before. Both inner edges of tires were down to cords. Well, tread was gone so they looked like slicks anyways. Drivers side had really bad wheel bearing but good upper joint. Pass side has good bearing but bad upper joint. I did a quick wheel adjustment to center steering wheel.

I had a pair of steel rims/tires with 200 miles on them handy.
I put them on the front after I did the repairs. Drove car for a few days. Seemed ok.
Than this weekend I swapped rear alloy wheels/tires front to rear. Still seemed ok.
Than I did the control arm. And that’s when the vibration showed up.
I plan on getting a pair of tires for the original alloys that I am not using now.

Than I did the control arm. And that’s when the vibration showed up.
I plan on getting a pair of tires for the original alloys that I am not using now.

Are you sure you did not get one of wheels slightly off when bolting it on?

Once a tire shop managed to attach one of my wheels the way entire car was shaking like in agony at certain speed.
Getting lug nuts loosened, then carefully re-tightening in criss-cross manner made it smooth again for me, so every time I bring car to tire place now, I’m re-doing their work back home. Sometimes they would make torque to be 1.5x of the recommended one, sometimes they would not tighten it enough

I read a bit online about Honda ball joint design where the lower ball joint is in separation/tension so if it fails, your wheel goes sideways. I wondered why there was a c-clip in area between knuckle/control arm while the oem does not have a c-clip. the tension is always pulling balljoint down into knuckle so the c-clip does nothing.